By SANDEEP JUNNARKAR

The scientists, working at the University of Rochester, took the drops of DNA, the double-helix coding for genes, and mixed them in a test tube to create a type of rudimentary computer that they hope could one day mature into one of the most powerful computers -- at least in terms of processing speeds.

Animesh Ray, an assistant professor in biology, and Mitsunori Ogihara, an assistant professor of computer science, both at the University of Rochester, teamed up to successfully use deoxyribonucleic acid, or DNA, to mimic a vital component found in all computers.

Instead of using electrical impulses -- a technique used in all digital computers -- to control the commands a processor gives to a computer, Ray and Ogihara used nucleotides, the basic units of DNA, to replicate the actions of a processor.

But don't expect to own a bubbling test-tube computer to run your spread sheets and word-processing applications. Researchers looking into the potential of molecular computation agree that even a pre-Pentium computer would easily outperform a DNA computer trying to perform simple tasks currently done on PCs.

So what is the value in DNA computing?

The molecular model, while it may not excel at simple tasks like word processing, could far more effectively tackle complex mathematical problems. In addition, a DNA computer could be much smaller and faster than digital computers.

Currently the world's most powerful supercomputer sprawls across nearly 150 square meters at the U.S. government's Sandia National Laboratories in New Mexico. But a DNA computer has the potential to perform the same breakneck-speed computations in a single drop of water.

"The merit exists in the fact that DNA molecules are so small that potentially one liter of DNA solution can store 10 to the 21st bits of information, which is gigantic." Ogihara said. "The maximum memory of digital computers is approximately 10 to the 15th. Obviously, a computer with that kind of memory is a supercomputer."

Molecular computation also offers the important benefits of high-speed chemical reactions and a virtually non-existent electrical power requirement.

But there are drawbacks.

Ray and Ogihara spent approximately $300 to create their rudimentary DNA computer on which they ran their experiments. "But an advanced DNA computer is not going to come cheap," Ray said. "The prohibitive step right now is the scaling up of DNA computer."

Ray's other concern is determining what practical role this computer will serve.

"Let me be bold enough now and say I don't know how exactly this is going to be applied," Ray said. "My feeling is that it won't be a word processor. Code breaking is a possibility. Solving large problems for major businesses like telecommunications companies or airline companies who want to optimize their airline routes may want to use a DNA computer."

Courtesy University of Rochester

Animesh Ray

Ogihara admits that DNA computers will have a viable future only if researchers can find situations in which molecular computers not only outperform digital computers, but in which digital computers would be unable to tackle the problems efficiently.

"This does not have to be a commercial application, but researchers must show that DNA computers can solve problems that we cannot hope to solve using digital computers," Ogihara said. "This is one of the most important issues in the study of DNA computers. Not only is building the computer important, but finding problems that only it can solve is also critical."

The Department of Defense already sees great potential in molecular computers. Its research wing, the Defense Advanced Research Project Agency, or DARPA, has taken a keen interest in DNA computing and is financing a consortium of research groups studying molecular computation.

"In general DOD tends to be an incredible consumer of information technology, especially if it means increased processing power and speed," said Jan Walker, a spokeswoman at DARPA. "We can only get so much from conventional designs."

She said DARPA could not predict when DNA computers will be routinely used. But the agency does envision a time when what it terms as ultra scale computers, which include DNA computers, could have denser memory and faster retrieval.

According to Walker, these systems could be used for among other things, image analysis and interpretation, and in the future version of military Stealth aircraft, which will be equipped with radar systems requiring huge processing power to analyze and reconstruct complex surfaces to their smallest details.

Courtesy University of Rochester

Mitsunori Ogihara

But that level of computing power is still years away.

"We have only been working on DNA computers for the past three years and it has to be understood that molecular computation is still embryonic," said Dr. Leonard Adleman, a professor of computer science at University of Southern California who in 1994 was the first to publish a paper describing how a DNA computer could be built to solve complex mathematical problems. "The greatest effort was spent in the first couple of years studying the theoretical aspects to determine if there were any reasons in principle why molecular computations could not work."

The questions raised included decisive concerns like whether an impractical amount of DNA would be required to realize the computational potential.

"The theoretical work dispelled any proposed reasons why it would not work in principle. That happened very quickly and was very pleasing," Adleman said. "Now we are transitioning into the lab to see if we can actually build these things in such a way that they will do a good job."

There are many alternative experimental theories to create competing ultra scale models. One is Intelligent Simulation, in which "thinking" systems autonomously design, monitor, and understand complex physical problems by a combination of computing approaches. Another method is Quantum Computation, in which single photon pulses replace today's electrical pulses, and in which individual atoms serve as memory storage devices. Many other approaches also involve a combination of computer science, physics and biotechnology.

David Gifford, a professor of computer science and engineering at the Massachusetts Institute of Technology, finds it difficult to favor one experimental approach over the others. "It is a completely different way of thinking about problems that we really don't understand very well yet," he said.

The work to understand molecular computation is intensifying.

There are several labs across the United States working on different DNA computers designs that are nevertheless based on the same principles -- that DNA can be used to store information, and this memory can be manipulated by a set of instructions.

"By the time we get to the year 2050, we'll have computers that are very different from what we have now in the silicon based chip," Adleman said. "If those changes are going to take place, it's worthwhile to look out very futuristically at different ways of doing computation."

Perhaps the DNA computer is the unifying theory of computation that combines the most efficient aspects of supercomputers like IBM's Deep Blue, the recent chess champion, and of living organisms to form a machine with limitless potential.

"For me, it also goes beyond computation and enters the area where we can study the relationship between computer technology, computer science, mathematics, biology and biotechnology," Adleman said. "A lot of people believe that there is such a rich interface between these huge disciplines. So this is a very broad path of which only one avenue is DNA computing.''

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